Bidirectional stent and method of use thereof

ABSTRACT

A bidirectional twistable stent is disclosed. The stent comprises a cylinder-shaped stent body having a plurality of axially arranged rows of struts encircling a central lumen and a plurality of flex connectors that connect at least two adjacent rows of struts in such a manner that allows the stent to be twisted clockwise or counter clockwise without causing deformation of any struts in the stent body. Also disclosed are the method of making the stent, method of using the stent, and a kit containing the stent.

This application is a Continuation of U.S. application Ser. No.15/165,917, which is a Continuation of U.S. application Ser. No.14/163,728, filed Jan. 24, 2014. Now U.S. Pat. No. 9,375,810. Theentirety of the aforementioned application is incorporated herein byreference.

FIELD

The present application relates generally to medical devices and, inparticular, to a stent implantable into a body cavity and method forimplanting same.

BACKGROUND

An in vivo supporting device or barrier device, such as a stent, is aman-made “tube” or “frame” inserted into a natural passage or conduit inthe body to prevent, or counteract, a disease-induced, localized flowconstriction or flow outflow like a leak or aneurysm. Supporting stentsinclude vascular supporting stents, non-vascular supporting stents, andaneurysm sealing stents. Vascular supporting stents are designed forapplications in the vascular system, such as arteries and veins.Non-vascular supporting stents are used in other body lumens such asbiliary, colorectal, esophageal, ureteral and urethral tract, and upperairway. Aneurysm sealing stents are used to close off potentiallydangerous aneurysms or pseudo aneurysms throughout the vascular andnon-vascular system.

Percutaneous transluminal angioplasty (PTA) has evolved over the past 20years to become a common therapeutic technique for the treatment ofperipheral vascular disease. Self-expanding stents are delivered to adesired site mounted onto a stent delivery catheter and are held inplace on the catheter by an outer cover until the stent has reached thedeployment site. The outer cover is retracted and the stent expands offthe catheter to contact the walls of the lumen, where it is held inplace by the chronic outward pressure of the stent against the walls ofthe lumen.

There are several problems with self-expanding stents currently on themarket, including the fact that their design takes into account onlytheir expansion at the site of deployment, without regard to thetwisting and bending that the stent must do to navigate blood vessels onthe way to the deployment site, which can cause the stent to collapse,resulting in damage to the stent that impairs proper deployment.Additionally, there exists the possibility of the stent foreshortening,displacing or jumping during deployment, causing the stent to beemplaced improperly, requiring removal of the stent and replacement withanother.

Therefore, there is an existing need for a self-expanding stent that,irrespective of the insertion site, is capable of enduring the twistinginherent in the delivery process and that evenly expands at thedeployment site without foreshortening.

SUMMARY

One aspect of the present application relates to a bidirectional stent,comprising: (1) a cylinder-shaped stent body comprising a plurality ofaxially arranged rows of struts encircling a central lumen, wherein eachof said rows of struts comprises struts inter-connected to form awave-pattern with alternating peaks and troughs, wherein each peak has atip and each trough has a bottom, and wherein said rows of struts formone or more row sections and wherein each row section comprises at leastone row of struts; (2) non-flex connectors that connect adjacent rows ofstruts within each row section, wherein each of said non-flex connectorscomprises a first end and a second end, wherein said first end isattached to a tip of a peak in a first row of struts, wherein saidsecond end is attached to a tip of a peak in a second row of struts,wherein said first row of struts and said second row of struts arewithin the same row section and are adjacent to each other, and whereinno non-flex connector is present in a row section containing only onerow of struts; and (3) flex connectors that connect adjacent rowsections, wherein each of said flex connectors comprises a first end anda second end, wherein said first end is attached to a bottom of a firsttrough in an edge row of struts of a first row section, said firsttrough has a first trough amplitude, wherein said second end is attachedto a bottom of a second trough in an edge row of struts of a second rowsection, said second trough has a second trough amplitude, wherein saidfirst row section is adjacent to said second row section, and whereinsaid stent body is capable of being twisted clockwise orcounter-clockwise from one end of said stent body by one-fourth of aturn, or more, without causing deformation of struts and connectors insaid stent body.

Another aspect of the present application relates to a bidirectionalstent, comprising: (1) a cylinder-shaped stent body comprising aplurality of axially arranged rows of struts encircling a central lumen,wherein each of said rows of struts comprises struts inter-connected toform a wave-pattern with alternating peaks and troughs, wherein eachpeak has a tip and each trough has a bottom; and (2) a first set of flexconnectors that connect a first pair of adjacent rows of struts and asecond set of flex connectors that connect a second pair of adjacentrows of struts, wherein each of said flex connectors has an s-shapedconnector body with a rotation orientation and connects a tip of a peakin one row of struts in a pair of adjacent rows of struts to a tip of apeak in another row of struts in the same pair of rows of struts,wherein flex connectors in the same set of flex connectors have the samerotation orientation, and wherein said first set of flex connectors havea rotation orientation that is opposite to the rotation orientation ofsaid second set of flex connectors, wherein said cylinder-shaped stentbody is capable of reversibly transforming into a peristaltic shape whentwisted clockwise or counter clockwise by one-fourth of a turn, or more,without causing permanent deformation of said stent body.

Another aspect of the present application relates to a bidirectionalstent, comprising: (1) a cylinder-shaped stent body comprising aplurality of axially arranged row of struts encircling a central lumen;and (2) flex connectors that connect at least two adjacent rows ofstruts in such a manner that allows said stent body to be twistedclockwise or counter-clockwise from one end of said stent body by halfof a turn, or more, without causing deformation of struts and connectorsin said stent body.

Another aspect of the present application relates to a bidirectionalstent, comprising: (1) a cylinder-shaped stent body comprising aplurality of axially arranged row of struts encircling a central lumen;and (2) flex connectors that connect at least two adjacent rows ofstruts in such a manner that allows said stent body to be twistedclockwise or counter-clockwise from one end of said stent body by halfof a turn, or more, without causing permanent deformation of said stentbody.

Another aspect of the present application relates to a method for makingthe stent of the present application, comprising: slitting acylinder-shaped tube with a laser to create a matrix of struts andconnectors that form a stent body.

Another aspect of the present application relates to a method of usingthe stent of the present application, comprising: placing the stent ofthe present application in a treatment site in a compressed state; andenlarging said stent to an expanded state at said treatment site toimmobilize said stent in a lumen, wherein said stent can be rotationallytwisted in either direction without deformation.

Another aspect of the present application relates to a stent kit,comprising: the bidirectional stent of the present application,instructions for using the stent and optionally, a guidewire.

Further objectives, features and advantages of the invention will beapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purposes of this disclosure, unless otherwise indicated,identical reference numerals used in different figures refer to the samecomponent.

FIG. 1 is a photograph of an embodiment of a bidirectional stent of thepresent application.

FIG. 2 shows a schematic representation of the strut and connectorstructure of the stent in FIG. 1 .

FIG. 3 shows a detailed view of the flex connector of the stent in FIG.1 .

FIG. 4 shows a schematic representation of twisting the stent of FIG. 1to the left.

FIG. 5 is a photograph of the stent of FIG. 1 being twisted to the left.

FIG. 6 shows a schematic representation of twisting the stent of FIG. 1to the right.

FIG. 7 is a photograph of the stent of FIG. 1 being twisted to theright.

FIGS. 8A-I show the results of a test comparing the bidirectionaltwistability of the stent of FIG. 1 to the twistability of severalcommercially available expandable stents.

FIG. 9 shows a comparison of the amount of force required to bend thestent of the present application and several commercially availablestents.

FIG. 10 shows a comparison of the deployment accuracy of the stent ofthe present application and several commercially available stents.

FIG. 11 shows a comparison of the foreshortening of the stent of thepresent application and several commercially available stents.

FIG. 12 is a photograph of another embodiment of a bidirectionalself-expanding stent of the present application.

FIG. 13 depicts the stent of FIG. 12 being twisted to the right.

FIG. 14 shows the twisted stent of FIG. 13 with the ends pushed inward

FIG. 15 shows the peristaltic effect of twisting/compressing the stentof FIG. 14 .

FIG. 16 also shows the peristaltic effect of twisting/compressing thestent of FIG. 14 .

FIG. 17 shows the stent of FIG. 12 with a stretchable electrospuncovering.

FIG. 18 shows the covered embodiment of FIG. 17 twisted towards theleft.

FIG. 19 shows the twisted covered stent of FIG. 18 having the ends ofthe twisted stent have been pushed towards each other inwards.

FIG. 20 shows the continued twisting of the covered stent.

DETAILED DESCRIPTION

The following detailed description is presented to enable any personskilled in the art to make and use the invention. For purposes ofexplanation, specific nomenclature is set forth to provide a thoroughunderstanding of the present invention. However, it will be apparent toone skilled in the art that these specific details are not required topractice the invention. Descriptions of specific applications areprovided only as representative examples. The present invention is notintended to be limited to the embodiments shown, but is to be accordedthe widest possible scope consistent with the principles and featuresdisclosed herein.

It is appreciated that certain features of the invention, which are forclarity described in the context of separate embodiments may also beprovided in combination in a single embodiment. Conversely variousfeatures of the invention, which are for brevity, described in thecontext of a single embodiment, may also be provided separately and/orin any suitable sub-combination.

One aspect of the present application relates to a bidirectional stent,comprising: a cylinder-shaped stent body comprising a plurality ofaxially arranged rows of struts encircling a central lumen, wherein eachof said rows of struts comprises struts inter-connected to form awave-pattern with alternating peaks and troughs, wherein each peak has atip and each trough has a bottom, and wherein said rows of struts formone or more row sections and wherein each row section comprises at leastone row of struts; non-flex connectors that connect adjacent rows ofstruts within each row section, wherein each of said non-flex connectorscomprises a first end and a second end, wherein said first end isattached to a tip of a peak in a first row of struts, wherein saidsecond end is attached to a tip of a peak in a second row of struts,wherein said first row of struts and said second row of struts arewithin the same row section and are adjacent to each other, and whereinno non-flex connector is present in a row section containing only onerow of struts; and flex connectors that connect adjacent row sections,wherein each of said flex connectors comprises a first end and a secondend, wherein said first end is attached to a bottom of a first trough inan edge row of struts of a first row section, said first trough has afirst trough amplitude, wherein said second end is attached to a bottomof a second trough in an edge row of struts of a second row section,said second trough has a second trough amplitude, and wherein said firstrow section is adjacent to said second row section, wherein said stentbody is capable of being twisted clockwise or counter-clockwise from oneend of said stent body by one-fourth of a turn, or more, without causingdeformation of any struts, non-flex connectors and flex-connectors insaid stent body.

In some embodiments each of said flex connectors comprises: a first armcomprising said first end, wherein said first arm has a length that isthe same as, or longer than said first trough amplitude; a second armcomprising said second end, wherein said second arm has a length that isthe same as, or longer than said second trough amplitude; and a middlesection connecting said first arm to said second arm, wherein saidmiddle section forms a first angle with said first arm and a secondangle with said second arm, wherein said first angle is in a range ofabout 90-160 degrees and wherein said second angle is in a range ofabout 90-160 degrees. In a further embodiment, said first angle is in arange of about 90-120 degrees and wherein said second angle is in arange of about 90-120 degrees.

In another embodiment, each row section contains two or more rows ofstruts. In a further embodiment each row section contains two rows ofstruts. In another further embodiment, each row of struts is connectedto an adjacent row of struts within the same row section by three ormore non-flex connectors.

In another embodiment, the stent body contains three or more rowsections. In a further embodiment, each row section is connected to anadjacent row section by three or more flex connectors.

In still another embodiment, peaks in the same row of struts have thesame peak amplitude and wherein troughs in the same row of struts havethe same trough amplitude.

In yet still another embodiment, each of the non-flex connectors has alength that is smaller than the row width of any of the two rows of thestruts connected by said non-flex connector.

In another embodiment the struts, the non-flex connectors and flexconnectors are made from a metal or an alloy.

In still another embodiment, said struts, said non-flex connectors andsaid flex connectors are made from nitinol.

In yet another embodiment, said stent body is coated with a polymericmaterial. In a further embodiment said polymeric material is abiodegradable material.

In another embodiment, said flex connectors allow said stent body to betwisted clockwise or counter-clockwise from one end of said stent bodyby ¼ of a turn without causing deformation of any struts and connectorsin said stent body.

In still another embodiment, said flex connectors allow said stent bodyto be twisted clockwise or counter-clockwise from one end of said stentbody by ½ of a turn without causing any deformation of said struts insaid stent body.

In yet still another embodiment, said flex connectors allow said stentbody to be twisted clockwise or counter-clockwise from one end of saidstent body by a full turn without causing any deformation of said strutsin said stent body.

Another aspect of the present application relates to a bidirectionalstent, comprising: a cylinder-shaped stent body comprising a pluralityof axially arranged rows of struts encircling a central lumen, whereineach of said rows of struts comprises struts inter-connected to form awave-pattern with alternating peaks and troughs, wherein each peak has atip and each trough has a bottom; and a first set of flex connectorsthat connect a first pair of adjacent rows of struts and a second set offlex connectors that connect a second pair of adjacent rows of struts,wherein each of said flex connectors has an s-shaped connector body witha rotation orientation that connects a tip of a peak in one row ofstruts in a pair of adjacent rows of struts to a tip of a peak inanother row of struts in the same pair of adjacent rows of struts,wherein flex connectors in the same set of flex connectors have the samerotation orientation, and wherein said first set of flex connectors havea rotation orientation that is opposite to the rotation orientation ofsaid second set of flex connectors, wherein said stent is capable ofreversibly transforming into a peristaltic shape when twisted clockwiseor counter clockwise by one-fourth of a turn, or more, without causingpermanent deformation of the stent body.

In some embodiments, each of said plurality of axially arranged rows ofstruts has a row amplitude and wherein each of said flex connectors hasa length that is greater than the row amplitudes of the two rows ofstruts that are connected by said flex connector. In a furtherembodiment, each of said flex connectors has a length that is about 150%to 500% of the larger of the row width of the two rows of struts thatare connected by said flex connectors. In a still further embodiment,each of said flex connectors has a length that is about 300% of thelarger of the row width of the two rows of struts that are connected bysaid flex connectors.

In another embodiment, said stent body is covered with a biodegradablecoating. In a further embodiment, said biodegradable coating compriseschitosan.

Yet another aspect of the present application relates to a bidirectionaltwistable stent, comprising: a cylinder-shaped stent body comprising aplurality of axially arranged rows of struts encircling a central lumen;and flex connectors that connect at least two adjacent rows of struts insuch a manner that allows said stent body to be twisted clockwise orcounter-clockwise from one end of said stent body by half of a turn, ormore, without causing deformation of said struts in said stent body.

In some embodiments, said stent body can be twisted clockwise orcounter-clockwise from one end of said stent body by a full turn withoutcausing deformation of said struts in said stent body.

In other embodiments, said stent body can be twisted clockwise orcounter-clockwise from one end of said stent body by two full turnswithout causing deformation of said struts in said stent body.

Still another aspect of the present application relates to abidirectional twistable stent, comprising: a cylinder-shaped stent bodycomprising a plurality of axially arranged rows of struts encircling acentral lumen; and flex connectors that connect at least two adjacentrows of struts in such a manner that allows said stent body to betwisted clockwise or counter-clockwise from one end of said stent bodyby half of a turn, or more, without causing permanent deformation ofsaid stent body.

In some embodiments, said stent body can be twisted clockwise orcounter-clockwise from one end of said stent body by a full turn withoutcausing deformation of said struts in said stent body.

In other embodiments, said stent body can be twisted clockwise orcounter-clockwise from one end of said stent body by two full turnswithout causing deformation of said struts in said stent body.

Another aspect of the present invention relates to a method for making abidirectional stent, comprising: a cylinder-shaped stent body comprisinga plurality of axially arranged rows of struts encircling a centrallumen, wherein each of said rows of struts comprises strutsinter-connected to form a wave-pattern with alternating peaks andtroughs, wherein each peak has a tip and each trough has a bottom, andwherein said rows of struts form one or more row sections and whereineach row section comprises at least one row of struts; non-flexconnectors that connect adjacent rows of struts within each row section,wherein each of said non-flex connectors comprises a first end and asecond end, wherein said first end is attached to a tip of a peak in afirst row of struts, wherein said second end is attached to a tip of apeak in a second row of struts, wherein said first row of struts andsaid second row of struts are within the same row section and areadjacent to each other, and wherein no non-flex connector is present ina row section containing only one row of struts; and flex connectorsthat connect adjacent row sections, wherein each of said flex connectorscomprises a first end and a second end, wherein said first end isattached to a bottom of a first trough in an edge row of struts of afirst row section, said first trough has a first trough amplitude,wherein said second end is attached to a bottom of a second trough in anedge row of struts of a second row section, said second trough has asecond trough amplitude, and wherein said first row section is adjacentto said second row section, wherein said stent body is capable of beingtwisted clockwise or counter-clockwise from one end of said stent bodyby one-fourth of a turn, or more, without causing deformation of anystruts, non-flex connectors and flex-connectors in said stent body, saidmethod comprising: slitting a cylinder-shaped tube with a laser tocreate a matrix of struts and connectors that form the stent body.

In some embodiments, said cylinder-shaped tube is made from a metal oran alloy.

In other embodiments, said cylinder-shaped tube is made from nitinol.

In another embodiment, the method comprises coating said matrix ofstruts and connectors with a biodegradable polymer coating.

In still another embodiment, the method further comprises covering saidmatrix of struts and connectors with a biodegradable polymer.

Another aspect of the present application relates to a method of using abidirectional stent, comprising: a cylinder-shaped stent body comprisinga plurality of axially arranged rows of struts encircling a centrallumen, wherein each of said rows of struts comprises strutsinter-connected to form a wave-pattern with alternating peaks andtroughs, wherein each peak has a tip and each trough has a bottom, andwherein said rows of struts form one or more row sections and whereineach row section comprises at least one row of struts; non-flexconnectors that connect adjacent rows of struts within each row section,wherein each of said non-flex connectors comprises a first end and asecond end, wherein said first end is attached to a tip of a peak in afirst row of struts, wherein said second end is attached to a tip of apeak in a second row of struts, wherein said first row of struts andsaid second row of struts are within the same row section and areadjacent to each other, and wherein no non-flex connector is present ina row section containing only one row of struts; and flex connectorsthat connect adjacent row sections, wherein each of said flex connectorscomprises a first end and a second end, wherein said first end isattached to a bottom of a first trough in an edge row of struts of afirst row section, said first trough has a first trough amplitude,wherein said second end is attached to a bottom of a second trough in anedge row of struts of a second row section, said second trough has asecond trough amplitude, and wherein said first row section is adjacentto said second row section, wherein said stent body is capable of beingtwisted clockwise or counter-clockwise from one end of said stent bodyby one-fourth of a turn, or more, without causing deformation of anystruts, non-flex connectors and flex-connectors in said stent body,comprising: placing the stent in a treatment site in a compressed state;and enlarging said stent to an expanded state at said treatment site toimmobilize said stent, wherein said stent can be rotationally twisted ineither direction at said treatment site without deformation of saidstent. In some embodiments, a stent of the present applicationforeshortens upon deployment less than 1% from its length in itscompressed state. In other embodiments, a stent of the presentapplication foreshortens upon deployment less than 0.9, 0.8, 0.7, 0.6,0.5, 0.4, 0.3, 0.2 or 0.1% from its length in its compressed state.

In some embodiments, said stent can be rotationally twisted at least onequarter turn in either direction at said treatment site withoutdeformation of said stent.

In other embodiments, said stent can be rotationally twisted at leastone half turn in either direction at said treatment site withoutdeformation of said stent.

In still other embodiments, said stent can be rotationally twisted atleast one full turn in either direction at said treatment site withoutdeformation of said stent.

Still another aspect of the present application relates to a stent kit,comprising: a bidirectional stent, the stent comprising: acylinder-shaped stent body comprising a plurality of axially arrangedrows of struts encircling a central lumen, wherein each of said rows ofstruts comprises struts inter-connected to form a wave-pattern withalternating peaks and troughs, wherein each peak has a tip and eachtrough has a bottom, and wherein said rows of struts form one or morerow sections and wherein each row section comprises at least one row ofstruts; non-flex connectors that connect adjacent rows of struts withineach row section, wherein each of said non-flex connectors comprises afirst end and a second end, wherein said first end is attached to a tipof a peak in a first row of struts, wherein said second end is attachedto a tip of a peak in a second row of struts, wherein said first row ofstruts and said second row of struts are within the same row section andare adjacent to each other, and wherein no non-flex connector is presentin a row section containing only one row of struts; and flex connectorsthat connect adjacent row sections, wherein each of said flex connectorscomprises a first end and a second end, wherein said first end isattached to a bottom of a first trough in an edge row of struts of afirst row section, said first trough has a first trough amplitude,wherein said second end is attached to a bottom of a second trough in anedge row of struts of a second row section, said second trough has asecond trough amplitude, and wherein said first row section is adjacentto said second row section, wherein said stent body is capable of beingtwisted clockwise or counter-clockwise from one end of said stent bodyby one-fourth of a turn, or more, without causing deformation of anystruts, non-flex connectors and flex-connectors in said stent body; andinstructions for using the stent.

In some embodiments, the kit further comprises a guidewire.

Bidirectional Stent

One aspect of the present application relates to a bidirectional stent.Specifically, the stent may be twisted clockwise or counter clockwise byone-fourth of a turn, one-half of a turn, or a full turn without causingdeformation of struts and connectors in the stent. As used herein, theterm “stent” refers to a device which is implanted within a bodily lumento hold open the lumen or to reinforce a small segment of the lumen.Stents include vascular and non-vascular stents. Vascular stents aredesigned for applications in the vascular system, such as arteries andveins. Non-vascular stents are used in other body lumens such asbiliary, colorectal, esophageal, ureteral and urethral tract, and upperairway. Non-limiting uses for stents include treating obstructed vesselsor lumens; occluding perforations, fistulas, ruptures, dehiscence,punctures, incisions, or aneurisms; and/or for delivering various drugsthrough controlled release to the particular lumen of interest.

In some embodiments, the bidirectional stent comprises a cylinder-shapedstent body having a plurality of axially arranged rows of strutsencircling a central lumen and a plurality of flex connectors. Each ofthe rows of struts comprises struts inter-connected to form awave-pattern or zig-zag pattern with alternating peaks and troughs. Eachpeak has a tip which is the highest point of the peak and defines a peakamplitude for that peak. Each trough has a bottom or nadir which is thelowest point in the trough and defines a trough amplitude for thattrough.

As used herein, the term “bidirectional” refers to a stent that iscapable of being twisted to the right (i.e., clockwise) and to the left(i.e., counter clockwise) at one end for one-fourth of a turn, one-halfof a turn, or a whole turn without causing deformation of the stentstructure elements (such as struts and connectors) or without causingpermanent deformation of the stent. As used herein “twisted at one end”means to attach one end of a stent to a support and rotate the other endof the stent clockwise or counter clockwise.

As used herein, the term “permanent deformation” or “irreversibledeformation” refers to a torsion-induced deformation of a stentstructure that is not reversible (i.e., returning to the pre-torsionform) after the removal of the torsion.

As used herein, the term “peak amplitude” refers to the verticaldistance between the tip of a peak and the nadir of an adjacent trough.If the two troughs flanking a peak have different depth, the “peakamplitude” of that peak is the vertical distance between the tip of thepeak and the nadir of the deeper trough flanking that peak.

As used herein, the term “trough amplitude” refers to the verticaldistance between the nadir of a trough and the tip of an adjacent peak.If the two peaks flanking a trough have different height, the “troughamplitude” of that trough is the vertical distance between the nadir ofthe trough and the tip of the higher peak flanking that trough.

As used herein, the “row width” of a row of struts is defined as thegreatest amplitude among the peak amplitudes and trough amplitudes inthat row of struts.

The rows of struts are connected to each other, either directly orthrough connectors. At least two adjacent rows of struts are connectedby the flex connectors. In some embodiments, adjacent rows of struts areconnected alternatively by the flex connectors and by non-flexconnectors (e.g., row 1 is connected to row 2 by flex connectors, row 2is connected to row 3 by non-flex connector element, row 3 is connectedrow 4 by flex connectors, row 4 is connected to row 5 by non-flexconnector element, and so forth). In other embodiments, adjacent rows ofstruts are connected alternatively by the flex connectors and by directconnection between the two adjacent rows (e.g., row 1 is connected torow 2 by flex connectors, row 2 is connected to row 3 directly, row 3 isconnected row 4 by flex connectors, row 4 is connected to row 5directly, and so forth). In some embodiments, every other row of strutsis connected to an adjacent row of struts with flex connect elements.

In some embodiments, rows of struts are connected directly or bynon-flex connectors to form row sections. The row sections are connectedto each other by flex connectors. In some embodiments, each row sectioncontains 2, 3, 4, 5, 6, 7, 8, 9 or 10 rows of struts and each stent bodycontains 2, 3, 4, 5, 6, 7, 8, 9, 10 or more row sections.

Suitable materials for the rows of struts, flex and non-flex connectorsinclude, but are not limited to, metal alloys such as nitinol. In someembodiments, the rows of struts, flex connectors and non-flex connectorsare made from the same material. In other embodiments, the rows ofstruts, flex connectors and non-flex connectors are made from differentmaterials.

Trough-to-Trough Flex Connections

In some embodiments, the flex connector element comprises a wire orstrut having a first end and a second end. The first end is attached toa bottom of a trough in one of the two adjacent rows of struts, and thesecond end is attached to a bottom of a trough in another of the twoadjacent rows of struts. The flex connector is composed of threesections: a first section that includes the first end and has a lengththat is equal to, or greater than, the trough amplitude of the troughthe first end is attached to; a second section that includes the secondend and has a length that is equal to, or greater than, the troughamplitude of the trough the second end is attached to; and a thirdsection that connects the first section to the second section. The thirdsection forms a first angle with the first section and a second anglewith the second section. In some embodiments, the first angle is in therange of about 90-160 degrees, 90-140 degrees or 90-120 degrees, and thesecond angle is in the range of about 90-160 degrees, 90-140 degrees or90-120 degrees. The first angle can be the same as, or different from,the second angle. In some embodiments, the first angle is about 90, 95,100, 105, 110, 115, 120, 125, 130, 135, 140 or 145 degrees, and thesecond angle is about 90, 95, 100, 105, 110, 115, 120, 125, 130, 135,140 or 145 degrees. In general, the angles are consistent in size andshape in order to allow for the concentric bidirectionality of thetwisting of the device in either direction. The flex connectors allowthe angles to collapse and fall into the connectors. In someembodiments, all the flex connectors in a stent body have the same totallength and/or shape. In other embodiments, the flex connectors in astent body have different total length and/or shape. In someembodiments, all the flex connectors connecting the same two rows ofstruts have the same total length and/or shape. As used herein, the term“total length” of a flex connector element is the distance between thefirst end and the second end of the flex connector element.

In some embodiments, the adjacent rows that are connected by the flexconnectors are connected by at least two flex connectors. In certainembodiments, the two adjacent rows are connected by 2, 3, 4, 5, 6, 7, 8,9 or 10 flex connectors.

In the embodiments with trough-to-trough flex connection, thetwistability of the stent body is determined by a combination of factorssuch as the number of adjacent rows of struts connected by the flexconnectors, the number of flex connectors used between two connectedrows of struts, the wave-configuration (e.g., the wave length andamplitude) of the rows of struts, the length of each section in each ofthe flex connectors and the total length and shape of the flexconnectors. In some embodiments, the stent body is configured such thatthe stent body can be twisted clockwise or counter-clockwise from oneend by one-fourth of a turn without causing deformation of struts andconnectors in the stent body. In other embodiments, the stent body isconfigured such that the stent body can be twisted clockwise orcounter-clockwise from one end by one-half of a turn without causingdeformation of struts and connectors in the stent body. In someembodiments, the stent body is configured such that the stent body canbe twisted clockwise or counter-clockwise from one end by a whole turnwithout causing deformation of struts and connectors in the stent body.

In some embodiments, the stent body is configured such that the stentbody can be twisted clockwise or counter-clockwise from one end byone-fourth of a turn without causing the deflection of the peaks outwardfrom the body of the stent more than 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10% ofthe distance of the diameter of the stent. For example, if a stent is 5mm in diameter, then a 10% outward deflection of a peak would mean thatsaid peak protrudes 0.5 mm from the outside of said stent. In otherembodiments, the stent body is configured such that the stent body canbe twisted clockwise or counter-clockwise from one end by one-half of aturn without causing the deflection of the peaks outward from the bodyof the stent more than 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10% of the distanceof the diameter of the stent. In some embodiments, the stent body isconfigured such that the stent body can be twisted clockwise orcounter-clockwise from one end by a whole turn without causing thedeflection of the peaks outward from the body of the stent more than 1,2, 3, 4, 5, 6, 7, 8, 9 or 10% of the distance of the diameter of thestent.

The term “non-flex connectors” are connectors that would not contributeto the twistability of the stent body. Examples of non-flex connectorsinclude, but are not limited to, short, straight struts that connect thetips of the peaks in a row of struts to the tips of the peaks in anadjacent row of struts. In some embodiments, two rows of struts areconnected directly to each other without the use of connectors byconnecting the tip of one or more peaks in one row to the tip of one ormore peaks in another row.

Peak-to-Peak Flex Connections

In some other embodiments, at least two pairs of adjacent rows of strutsare connected by flex connectors in a peak-to-peak manner. Thepeak-to-peak flex connector comprises a wire or strut having an offsetline profile and a rotation orientation. The offset is the result of adeflection (or jag) to one side or the other at about the mid-point inthe length of the flex connector. The deflection is in the samedirection in each of the flex connectors within a row. In someembodiments, the offset can only have one of the two rotationorientations: a left rotation orientation (i.e., similar to the profileof the letter “S”) or a right rotation orientation (i.e., similar to theprofile of the letter “Z”). One end of the peak-to-peak flex connectoris attached to a tip of a peak in one of the two adjacent rows of strut,and the other end is attached to a tip of a peak in another of the twoadjacent rows of strut. In this configuration, the peak-to-peak flexconnector has a total length that is greater than the row width ofeither of the two rows of struts connected by the peak-to-peak flexconnector. In some embodiments, the peak-to-peak flex connector has atotal length of about 150-200%, 150-250%, 150-300%, 150-350%, 150-400%,150-450%, 150-500%, 200-250%, 200-300%, 200-350%, 200-400%, 200-450%,200-500%, 250-300%, 250-350%, 250-400%, 250-450%, 250-500%, 300-350%,300-400%, 300-450%, 300-500%, 350-400%, 350-450%, 350-500%, 400-450%,400-500% or 450-500% of the row width of a row of struts that isconnected to the peak-to-peak flex connector.

The peak-to-peak flex connection requires that the peak-to-peak flexconnectors connecting a pair of adjacent rows of struts have the samerotation orientation. Further, the stent body must have at least onepair of adjacent rows of struts connected by peak-to-peak flexconnectors of left rotation orientation (left-connected pair) and atleast one pair of adjacent rows of struts connected by peak-to-peak flexconnectors of right rotation orientation (right-connected pair).Preferably, the stent contains an equal number of left-connected pairand right-connected pair so as to offer bidirectional twistability.

In some embodiments, all the flex connectors in the stent body withpeak-to-peak connection have the same total length and/or shape. Inother embodiments, the flex connectors in a stent body have differenttotal length and/or shape. In some embodiments, all the flex connectorsconnecting the same two rows of struts have the same total length and/orshape. In some embodiments, the adjacent rows that are connected bypeak-to-peak flex connectors are connected by at least two peak-to-peakflex connectors. In certain embodiments, the two adjacent rows areconnected by 2, 3, 4, 5, 6, 7, 8, 9 or 10 peak-to-peak flex connectors.

In a stent body containing peak-to-peak flex connectors, twisting thestent body to the left would cause the section of the stent bodyconnected by peak-to-peak flex connectors with left rotation orientationto contract, and the section of the stent body connected by peak-to-peakflex connectors with right rotation orientation to expand. Similarly,twisting the stent body to the right would cause the section of thestent body connected by peak-to-peak flex connectors with right rotationorientation to contract, and the section of the stent body connected bypeak-to-peak flex connectors with left rotation orientation to expand.Such contraction and expansion may also results in reversibledeformation of one or more flex connectors. The net effect of twistingis to reversibly transform the cylinder-shaped stent into a peristalticshape with alternating contracted sections and expanded sections. Thestent returns to its original cylinder shape when the torsion caused bythe twisting is removed.

In the embodiments with peak-to-peak flex connection, the twistabilityof the stent body is determined by a combination of factors such as thenumber of adjacent rows of struts connected by the flex connectors, thenumber of flex connectors used between two connected rows of struts, thewave-configuration (e.g., the wave length and amplitude) of the rows ofstruts, and the length of the flex connectors. In some embodiments, thestent body is configured such that the stent body can be twistedclockwise or counter-clockwise from one end by one-fourth of a turnwithout causing irreversible deformation of the stent body and/orirreversible deformation of any struts in the stent body. In otherembodiments, the stent body is configured such that the stent body canbe twisted clockwise or counter-clockwise from one end by one-half of aturn without causing irreversible deformation of the stent body and/orirreversible deformation of any struts in the stent body. In someembodiments, the stent body is configured such that the stent body canbe twisted clockwise or counter-clockwise from one end by a whole turnwithout causing irreversible deformation of the stent body and/orirreversible deformation of any struts in the stent body, nor anydeformation on the shape of the stent body.

Stent Covering or Coating

In some embodiments, a stent of the present application may be coveredor coated with a covering or coating material. The stent coating orcovering may be applied by any suitable method known in the art,including, but not limited to electrospinning, dip coating, spraying orfilm coating. In some embodiments, the stent may first be coated with afirst layer using one method, followed by coating with one or moreadditional layers using the same, or a different method. In someembodiments, the material used for the first layer is the same as thematerial used for at least one additional layer. In other embodiments,the material used for the first layer is different from the materialused for any additional layer.

The process of electrospinning can be carried out by any method known inthe art. The method used in the present invention is not to be limitedto a single method of electrospinning. Exemplary, non-limiting,processes for electrospinning are described, for example, by Yuan, X etal. (Yuan, X et al. Characterization of Poly-(L-Lactic Acid) FibersProduced by Melt Spinning. J. Appl. Polym, Sci. 2001, 81:251-260.) andin ZEUS Technical Newsletter, Electrospinning—Fibers at the Nano-scale.2009 (Zeus Industrial Products, Inc., Orangeburg, S.C.).

In the coating of the device by electrospinning, the device is coveredin a way that the fibers cross one another interlocking and formingangles. In one embodiment, the fibers intersect one another at angleswith angles from about 1, 5, 10, 15, 20, 25, 30, 35, 40 or 45 degrees toabout 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95 degrees. In anotherembodiment, the fibers intersect one another at angles with angles fromabout 1 degree to about 95 degrees. In a further embodiment, the fibersintersect one another at angles with angles from about 5 degrees toabout 95 degrees. In another embodiment, the fibers intersect oneanother at angles with angles from about 10 degrees to about 90 degrees.

The fibers are overlapped to allow for the stresses during crimping,loading, and expansion to be borne by all the materials filaments withthe stress loads being on the various filaments and their respectiveangles which allows the distribution of the stresses and the loads inall directions versus a uniform direction which is required for theopening and closing of a cylindrical tube of varying lengths. In oneembodiment, the fibers are overlapped a minimum of about 1 time and amaximum of about 1000 times. In a preferred embodiment, the fibers areoverlapped a minimum of about 1 time and a maximum of about 500 times.In another preferred embodiment, the fibers are overlapped a minimum ofabout 2 times and a maximum of about 500 times. Yet in another preferredembodiment, the fibers are overlapped a minimum of about 2 times and amaximum of about 400 times. In still another preferred embodiment, thefibers are overlapped a minimum of about 2 times and a maximum of about300 times. In a more preferred embodiment, the fibers are overlapped aminimum of about 2 times and a maximum of about 200 times. In a mostpreferred embodiment, the fibers are overlapped a minimum of 2 times anda maximum of 200 times.

In some embodiments, the stent is covered with a persistent,non-biodegradable polymer material. Examples of suitablenon-biodegradable covering materials include, but are not limited to,polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE),polyurethane (PU), silicones, or mixtures thereof.

In other embodiments, the covering of the stent can be made of abiodegradable or bioabsorbable material such as, but not limited to, apoly-(α-hydroxy acid), preferably poly-(L-lactic acid). In a furtherembodiment, the covering material can be mixed with barium sulphate orother illuminating material to insure proper placement and visibilityduring the deployment using fluoroscopy, x-ray, or other imagingmodalities.

In a particular embodiment, the biodegradable or bioabsorbable materialfor the covering of the stent is formulated to begin to degrade in noless than 15 days after the device is emplaced in the subject. Inanother embodiment, the biodegradable or bioabsorbable material for thecovering of the stent is formulated to begin to degrade in no less than30 days after the stent is emplaced in the subject. In a furtherembodiment, the biodegradable or bioabsorbable material for the coveringof the stent is formulated to begin to degrade in no less than 45 daysafter the stent is emplaced in the subject. In still another embodiment,the biodegradable or bioabsorbable material for the covering of thestent is formulated to begin to degrade in no less than 60 days afterthe stent is emplaced in the subject. In yet another embodiment, thebiodegradable or bioabsorbable material for the covering of the stent isformulated to begin to degrade in no less than 90 days after the stentis emplaced in the subject.

In a certain embodiment, the biodegradable or bioabsorbable material forthe covering of the stent is formulated to fully degrade within 90 daysafter the device is emplaced in the subject. In a further embodiment,the biodegradable or bioabsorbable material for the covering of thestent is formulated to fully degrade within 120 days after the stent isemplaced in the subject. In another embodiment, the biodegradable orbioabsorbable material for the covering of the stent is formulated tofully degrade within 150 days after the stent is emplaced in thesubject. In still another embodiment, the biodegradable or bioabsorbablematerial for the covering of the stent is formulated to fully degradewithin 180 days after the stent is emplaced in the subject. In yetanother embodiment, the biodegradable or bioabsorbable material for thecovering of the stent is formulated to fully degrade within one yearafter the stent is emplaced in the subject.

In one embodiment, the covering of the stent comprises a copolymer madefrom 34% lactide, 35% caprolactone, 14% trimethylene carbonate, and 17%glycolide. The copolymer may be deposited on the stent like body byelectrospinning or by film coating. The copolymer coating would providestrength retention for 30-60 days and mass absorption in 9-12 months.

Examples of biodegradable polymers include, but are not limited to,polydioxanone, polycaprolactone, polygluconate, poly(lactic acid)polyethylene oxide copolymer, modified cellulose, polyhydroxybutyrate,polyamino acids, polyphosphate ester, polyvalerolactone,poly-ε-decalactone, polylactonic acid, polyglycolic acid, polylactides,polyglycolides, copolymers of the polylactides and polyglycolides,poly-ε-caprolactone, polyhydroxybutyric acid, polyhydroxybutyrates,polyhydroxyvalerates, polyhydroxybutyrate-co-valerate,poly(1,4-dioxane-2,3-one), poly(1,3-dioxane-2-one), poly-para-dioxanone,polyanhydrides, polymaleic acid anhydrides, polyhydroxy methacrylates,fibrin, polycyanoacrylate, polycaprolactone dimethylacrylates,poly-β-maleic acid, polycaprolactone butyl acrylates, multiblockpolymers from oligocaprolactonediols and oligodioxanonediols, polyetherester multiblock polymers from PEG and poly(butylene terephthalates),polypivotolactones, polyglycolic acid trimethyl carbonates,polycaprolactone glycolides, poly(γ-ethyl glutamate),poly(DTH-iminocarbonate), poly(DTE-co-DT-carbonate), poly(bisphenolA-iminocarbonate), polyorthoesters, polyglycolic acid trimethylcarbonate, polytrimethyl carbonates, polyiminocarbonates,poly(N-vinyl)-pyrrolidone, polyvinyl alcohols, polyester amides,glycolized polyesters, polyphosphoesters, polyphosphazenes,poly[p-carboxyphenoxy)propane], polyhydroxy pentanoic acid,polyanhydrides, polyethylene oxide propylene oxide, soft polyurethanes,polyurethanes having amino acid residues in the backbone,polyetheresters such as polyethylene oxide, polyalkene oxalates,polyorthoesters as well as copolymers thereof, lipids, carrageenans,fibrinogen, starch, collagen, protein based polymers, polyamino acids,synthetic polyamino acids, zein, polyhydroxyalkanoates, pectic acid,actinic acid, carboxymethyl sulfate, albumin, hyaluronic acid, chitosanand derivatives thereof, heparan sulfates and derivates thereof,heparins, chondroitin sulfate, dextran, β-cyclodextrins, copolymers withPEG and polypropylene glycol, gum arabic, guar, gelatin, collagenN-hydroxysuccinimide, lipids, phospholipids, polyacrylic acid,polyacrylates, polymethyl methacrylate, polybutyl methacrylate,polyacrylamide, polyacrylonitriles, polyamides, polyetheramides,polyethylene amine, polyimides, polycarbonates, polycarbourethanes,polyvinyl ketones, polyvinyl halogenides, polyvinylidene halogenides,polyvinyl ethers, polyisobutylenes, polyvinyl aromatics, polyvinylesters, polyvinyl pyrrolidones, polyoxymethylenes, polytetramethyleneoxide, polyethylene, polypropylene, polytetrafluoroethylene,polyurethanes, polyether urethanes, silicone polyether urethanes,silicone polyurethanes, silicone polycarbonate urethanes, polyolefinelastomers, EPDM gums, fluorosilicones, carboxymethyl chitosanspolyaryletheretherketones, polyetheretherketones, polyethyleneterephthalate, polyvalerates, carboxymethylcellulose, cellulose, rayon,rayon triacetates, cellulose nitrates, cellulose acetates, hydroxyethylcellulose, cellulose butyrates, cellulose acetate butyrates, ethyl vinylacetate copolymers, polysulfones, epoxy resins, ABS resins, EPDM gums,silicones such as polysiloxanes, polydimethylsiloxanes, polyvinylhalogens and copolymers, cellulose ethers, cellulose triacetates,chitosans and copolymers and/or mixtures of the aforementioned polymers.

In a particular embodiment, the stent comprises visibility or opacitytechnology allowing visualization of the stent using an imaging means orimbedding the covering or strut coating with the same or various drugsor illuminating material. In some embodiments, the visibility or opacitytechnology comprises tantalum markers. In another embodiment, thecovering allows the stent to freely float or to move in a controlledmanner under the coating and covering, with the level of restrictiondepending on the thickness of said covering or coating. In anotherembodiment, the covering or coating has varying degrees of degradation.If the covering was formed by the electrospinning, the filaments wouldbe intertwined and set with such angles to allow the stent to be crimpedand opened as required in normal applications and the degradation couldbe controlled by the density of the material established by the numberof filament crossings and the angles to absorb the load and stresses ofopening and closing and anatomical compressions. Furthermore, thematerial of the support, coating and covering of the stent allow normalbody fluids to flow unobstructed. In yet another embodiment, the stentis covered in a single layer, double layer, triple layer or multiplelayers depending on the need. The covering can be on the outside of thestent like body, on the inside of the stent like body, or encapsulatingthe like body.

In another embodiment, the stent comprises a therapeutically effectiveamount of a therapeutic agent or agents. In particular embodiments, thestent comprises at least one therapeutic agent. In other embodiments,the stent comprises one therapeutic agent or more than one therapeuticagent. In still other embodiments, the stent comprises two, at leasttwo, three, four, or five therapeutic agents. In a particularembodiment, a therapeutic agent comprised on the stent is an analgesicor anesthetic agent. In another particular embodiment, a therapeuticagent comprised on the stent is an antibiotic, antimicrobial, antiviral,or antibacterial agent. In another embodiment, a therapeutic agentcomprised on the stent is a thrombotic or coagulant agent. In anotherembodiment, a therapeutic agent comprised on the stent is ananti-thrombotic or anticoagulant agent.

In certain embodiments, the therapeutic agent is comprised in apharmaceutical composition formulated for sustained-release.Sustained-release, also known as sustained-action, extended-release,time-release or timed-release, controlled-release, modified release, orcontinuous-release, employs a pharmaceutically acceptable agent thatdissolves slowly and releases the therapeutic agent over time. Asustained-release formulation allows the topical release of steadylevels of the therapeutic agent directly at the site where it would betherapeutically effective.

In one embodiment, the pharmaceutical composition is formulated forsustained release by embedding the active ingredient in a matrix ofinsoluble substance(s) such as acrylics or chitin. A sustained releaseform is designed to release the therapeutic agent at a predeterminedrate by maintaining a constant drug level for a specific period of time.This can be achieved through a variety of formulations, including, butnot limited to liposomes and drug-polymer conjugates, such as hydrogels.

In another embodiment, the therapeutic agent is comprised in apharmaceutical composition formulated for delayed-release, such that thetherapeutic agent is not immediately released upon administration. Anadvantage of a delayed-release formulation is that the therapeutic agentis not released from the stent until the stent has been emplaced in thedesired location. In some embodiments, the therapeutic agent is firstcoated onto the stent and is then coated over with a pharmaceuticalcomposition formulated for delayed-release.

In a particular embodiment, the therapeutic agent is delivered in avehicle that is both delayed release and sustained release.

In another embodiment, a therapeutic agent comprised on the stent isapplied to the exterior surface of the device. A therapeutic agent maybe applied to the exterior of the cover or may be mixed or imbedded intothe covering material. In some embodiments, the stent may contain anadditional coating on its exterior that delays the release of thetherapeutic agent or modulates the release of the therapeutic agent overtime. In one embodiment, the covering of the stent is further coatedwith a drug coating that can be eluted to minimize hyperplastic responseor to induce closure of the aneurysm.

In another embodiment, a therapeutic agent comprised on the stent isapplied to the interior surface of the stent. In further embodiments,therapeutic agents are applied to both the interior and to the exteriorsurfaces of the stent. Therapeutic agents applied to the interior andexterior surfaces of the stent may be the same or different. As anon-limiting example, a coagulant agent may be applied to the exteriorsurface of the stent to facilitate the healing of a perforation, whilean anti-coagulant may be applied to the interior of the stent to preventrestriction of the flow of bodily fluids and cells through the stent.

In some embodiments, the bidirectional twistable stent of the presentapplication is a self-expanding stent. The stent may be maintained in acompressed state by a wrapper or a restrainer. Upon removal of thewrapper or the restrainer, the stent spontaneously expands to anexpanded state that has a central lumen with a diameter that is greaterthan the diameter of the central lumen in the compressed state.

Kit

Another aspect of the present application relates to a bidirectionalstent kit. In some embodiments, the kit comprises one or morebidirectional stents and instructions on how to use the one or morebidirectional stents. In some embodiments, the kit further comprises onor more items selected from the group consisting of guide wires, radialintroducer sleeves, guide catheters, access closure devices, dilationballoons, suture materials and cutting instruments.

Method of Making the Stent

Another aspect of the present application relates to a method for makingthe stent of the present application. The stent of the presentapplication can be laser cut, water jet cut, stamped, molded, lathed orformed with other methods commonly used in the art. In some embodiments,the method comprises the steps of slitting a cylinder-shaped tube withlaser to create a matrix of struts and connectors that form the stentbody of the present application and coating the stent body with abiodegradable polymer coating. In some embodiments, the cylinder-shapedtube is made from a metal or an alloy, such as nitinol. In someembodiments, the method further comprises the step of coating the stentbody with a coating material as describe above. In some embodiments, thecoating is a biodegradable polymer coating.

Method of Using the Stent

Another aspect of the present application relates to a method of usingthe stent. The method comprises the steps of placing the expandablestent of the present application in a treatment site in a contractedstate and enlarging the stent to an expanded state at the treatment siteto immobilize the stent.

FIG. 1 is a picture of a self-expanding, bidirectional twistable stent100 of the present application. The stent 100 comprises a stent body 20that comprises rows 10 of struts 1. Adjacent rows 10 are connected byflex connectors 7 or non-flex connectors 5. FIGS. 2 and 3 are schematicrepresentations showing the matrix of struts 1 and connectors 5, 7 inthe stent body. As shown in FIG. 2 , the stent body comprise rows 10 ofstruts 1 that are joined end-to-end in the row 10 to form a wave patternhaving alternating peaks 8 and troughs 9. As used herein, the “peak” 8of each wave is on the outside of the wave pattern of each row 10.Inside each wave, opposite of the tip 2 of the peak 8, is the bottom ornadir 3 of the trough 9. Peaks 8 and troughs 9 face each way in the rows10. The end 4 of each row 10 is joined to the opposite end 4 of the samerow 10, such that each row 10 forms a ring encircling the central lumenof the stent. The rows 10 of struts may be connected to each other byeither non-flex connectors 5 or flex connectors 6.

In some embodiments, the flex connectors are aligned in such a way thatthey allow the troughs to collapse into the flex connector and flexconnectors are organized at intermittent patterns alternatively andcircumferentially around the stent. In particular embodiments, all flexconnectors are aligned going in one direction so that, uponcircumferential torsion, all the peaks or troughs line up in the correctgrove or saddle. When turned in the opposite direction, the same thinghappens but in the opposite direction, wherein the flex connectors inthe opposite direction are all aligned in one direction as well.

In some embodiments, each stent body comprises at least one row section15 of struts. In some embodiments, the row section 15 contains 2 rows 10of struts. In some embodiments, each row section 15 contains 1 row 10 ofstruts. In some embodiments, each row section 15 contains 3, 4, 5, 6, 7,8, or 10 rows 10 of struts. Each row of struts 10 within each rowsection 15 are joined together by the short, non-flex connectors 5 thatare attached to facing peaks 2 of adjacent rows 10 within the rowsection 15. In some embodiments, there are three connectors 5 joiningadjacent rows 10 over the entire length of the rows 10. In otherembodiments, there are 4, 5, 6, 7, 8, 9 or 10 non-flex connectors 5joining adjacent rows 10 over the entire length of the rows 10. In someembodiments, two adjacent rows 10 are joined by a non-flex connector 5at every third pair of facing peaks 2. In other embodiments, twoadjacent rows 10 are joined by a connector 5 at every second, fourth,fifth, sixth, seventh, eighth, ninth or tenth pair of facing peaks 2.

Still referring to FIG. 2 adjacent row sections 15 of stent body 20 arejoined to one another by flex connectors 6. In some embodiments, eachflex connector 6 is attached at one end to a nadir 3 of a trough in therow 10 at the edge of a section 15, and at the other end to a nadir 3 ofa trough in the row 10 at the edge of a facing row sections 15. The flexconnectors 6 are designed to absorb the torsional stress of twisting thestent. The length of the flex connectors 6 is such that the peaks 2along the outside of adjacent row section 15 do not contact each otherwhen the stent is not being twisted. In some embodiments, the flexconnector 6 contains a first arm 11, a second arm 12 and a crook or bend7 that connects the first arm 11 to the second arm 12. The crook 7 islocated at the center of each flex connector 6 and forms an angle withthe first arm 11 and the second arm 12. In some embodiments, the crook 7is positioned in the flex connector 6 so that it will clear a peak 2adjacent to the nadir 3 to which the flex connector 6 is attached whenthe stent is twisted.

In some embodiments, there are three flex connectors 6 joining adjacentrow sections 15 over the entire length of the row section 15. In otherembodiments, there are 4, 5, 6, 7, 8, 9 or 10 flex connectors 6 joiningadjacent row sections 15 over the entire length of the row section 15.In some embodiments, every third pair of facing nadir 3 at the outeredge of two adjacent row section 15 is connected by a flex connector 6.In other embodiments, every second, fourth, fifth, sixth, seventh,eighth, ninth or tenth pair of facing nadir 3 at the outer edge of twoadjacent row section 15 is connected by a flex connector 6.

In some embodiments, each flex connector 6 between two adjacent sections15 is offset at least one nadir 3 away from the peak 2 to which anon-flex connector 5 joining the rows 10 at the outer edge of said rowsection 15 to their adjacent rows 10 within said row section 15.

Furthermore, in some embodiments, each flex connector 6 between rowsection 15 is offset at least one nadir 3 away from the flex connector 6attached to a nadir 3 on the opposite edge of said row section 15.

Turning now to FIG. 3 , shown is a detailed view of a flex connector 6being joined at each end to a nadir 3 of a row 10 at the edge of a rowsection 15.

FIG. 4 is a schematic representation of the twisting of a stentrepresented by the schematic shown in FIG. 2 . In this case, the stentis twisted in a left-handed direction. Looking at the left-most row 10in the figure, the flex connector 6 bends to the side such that thecrook 7 in the flex connector 6 interdigitates with the peak 2 to theimmediate right of the nadir 3 to which it is attached.

FIG. 5 is a photograph of a stent comprising the structure detailed inthe schematic in FIG. 2 , twisted in a left-handed manner as describedfor FIG. 4 .

FIG. 6 is a schematic representation of the opposite twisting of a stentrepresented by the schematic shown in FIG. 2 . In this case, the stentis twisted in a right-handed direction. Looking at the left-most row 10in the figure, the flex connector 6 bends to the side such that thecrook 7 in the flex connector 6 forms a brace against the peak 2 to theimmediate left of the nadir 3 to which it is attached.

FIG. 7 is a photograph of a stent comprising the structure detailed inthe schematic in FIG. 2 , twisted in a right-handed manner as describedfor FIG. 6 .

FIGS. 8A-I show a comparison of twistability between a self-expandingstent as described in the present application and 3 expanding stentsthat are commercially available. The stents are each secured at the topto an immobile base and at the bottom to a turning axle. The axles arelinked together and turn the same distance in each figure. FIG. 8Adepicts the present stent (SES) and the commercially available stents(Competitor D, Competitor B and Competitor E) in a resting, untwistedstate. In FIG. 8B, the axle attached to each of the stents has beenturned ¼ turn to the left from the resting position in FIG. 8A, while inFIG. 8C the axle attached to each of the stents has been turned ¼ turnto the right from the resting position in FIG. 8A.

In FIG. 8D, the axle attached to each of the stents has been turned ½turn to the left from the resting position in FIG. 8A, while in FIG. 8Ethe axle attached to each of the stents has been turned ½ turn to theright from the resting position in FIG. 8A. As seen in FIGS. 8C and 8D,the stents D, B and E begin to deform from being a straight tube andthat this deformation is different for each of stents D, B and Edependent upon whether they are turned towards the left or the right,indicating that there is a unidirectionality to the way each of thosestents is designed. However present stent SES is able to turn in eitherdirection with equal ease, showing that the stent is bidirectional inits twistability.

In FIG. 8F, the axle attached to each of the stents has been turned ¾turn to the left from the resting position in FIG. 8A, while in FIG. 8Gthe axle attached to each of the stents has been turned ¾ turn to theright from the resting position in FIG. 8A. Each of stents D, B and Edeforms or collapses from being a straight tube and the effect is againdifferent for each of stents D, B and E dependent upon whether they areturned towards the left or the right. Accordingly, if these stents areplaced in a situation where they are placed under torsional stress, theyare likely to fail and will not be able to maintain an open passage.However present stent SES remains able to turn in either direction withequal ease, showing that torsional direction has no effect on itsability to maintain an open passage.

In FIG. 8H, the axle attached to each of the stents has been turned onefull turn to the left from the resting position in FIG. 8A, while inFIG. 8I the axle attached to each of the stents has been turned one fullturn to the right from the resting position in FIG. 8A. Each of stentsD, B and E completely collapses irrespective of whether they are turnedtowards the left or the right. However present stent SES remains able toturn in either direction with equal ease, showing that torsionaldirection has no effect on its ability to maintain an open passage.

If a stent is unidirectional, it will perform differently being emplacedthrough the right arm or leg versus being emplaced through the left armor leg because the shear stresses of moving through the vessels aredifferent. Furthermore, a unidirectional stent's performance is impactedby which end of the stent is mounted distally on the delivery catheterversus proximally. Therefore, a stent having a unidirectional designmust always be loaded onto the catheter in the same direction each timeand used in the same arm or leg (only left or only right) to ensureconsistent performance. Comparatively, the bidirectional stent of thepresent application, as shown in FIGS. 8A-I, is resistant to thedifference in torsional forces between left-handed and right-handedoperation, meaning that a single stent design can be used with equalperformance whether inserted on the right side or left side of thepatient's body.

FIG. 9 depicts the amount of force required in millinewtons (mN) to bendthe presently described stent (SES) and commercially available stents A,B, C, D, E, F1 and F2. Greater ease of flexibility allows the stent tobe more easily deployed through difficult bends in the vasculatureduring deployment.

FIG. 10 depicts the results of a deployment accuracy test of thepresently described stent (SES) and commercially available stents A, B,C, D, E, F1 and F2 under identical conditions. The present stentperformed as well as or better than the other stents in a measure ofdislocation of the stent during deployment, with all segments of thepresent stent opening uniformly and no overlapping of segments detected.

FIG. 11 depicts the results of a foreshortening test of the presentlydescribed stent (SES) and commercially available stents A, B, D, F1 andF2 under identical conditions. Foreshortening can occur when anexpandable stent is deployed from the delivery device, such as acatheter. During delivery, the stent is held in a compressed state onthe delivery device. When the stent is released from this compressedstate upon deployment, the open spaces between struts expand as thestruts move away from one another, with the diameter of the stentchanging from the compressed state around the delivery device to anexpanded state against the interior walls of the vessel or lumen. Asshown in FIG. 11 , this stent expansion causes stents A, B, D, F1 and F2to foreshorten between about 1 and 10% from their length in theircompressed state. However, the bidirectional stent of the presentapplication surprisingly foreshortens only about 0.1%, owing to itsnovel bidirectional design and flex connectors. Accordingly, theplacement accuracy of the present stent is higher than other expandablestents. In some embodiments, a stent of the present applicationforeshortens upon deployment less than 1% from its length in itscompressed state. In other embodiments, a stent of the presentapplication foreshortens upon deployment less than 0.9, 0.8, 0.7, 0.6,0.5, 0.4, 0.3, 0.2 or 0.1% from its length in its compressed state.

FIG. 12 is a photograph of another embodiment of a bidirectionalself-expanding stent of the present application, shown in a restingstate. This embodiment comprises single rows 10 of struts 1 that arejoined end-to-end in the row 10 to form a wave pattern havingalternating peaks and troughs. Each row 10 is joined completely around,such that each row 10 forms a ring encircling the central lumen of thestent. In this particular embodiment, each peak 2 (first peak) in a rowis attached to one end of a flexible connector 8 that, when the stent isin a resting state, is attached at its other end to a facing peak 2 ofan adjacent row 10, with said facing peak 2 being at an angle to thefirst peak. In some embodiments, said angle is between about 20 degreesand 70 degrees. In some further embodiments, said angle is between about30 degrees and 60 degrees. In a still further embodiment, said angle isabout 45 degrees. When twisted, the openings in this particularembodiment overlap. Depending upon the amount of overlap, theflexibility or pushability of the device can be changed. Further, thelength of the struts can be of any length in this embodiment, thusaltering the amount of overlap and affording great flexibility andcolumn strength. The interconnected nature of the overlap allows thebidirectional twisting of the stent.

FIG. 13 is a photograph of the embodiment of FIG. 12 , wherein the stenthas been twisted about ¼ turn to the right and elongated. The figureshows the relationship of the connectnedness of the shapes (formed bythe openings) that basically form a line followed by a cell followed bya line throughout the length of the stent. The interconnectedness ofthis gives it great column strength and allows for removability, whilethe stacked overlapping allows for changes of flexibility or stiffnessbased on the amount of the overlap.

FIG. 14 is a photograph of the embodiment pictured in FIG. 13 , whereinthe ends of the twisted stent have been pushed towards each other,causing the flexible connectors to bulge outwards. Twisting, pushing andpulling on (or of) sections of the stent are dependent upon thebiomechanics of the lumen in which the stent is placed, including (butnot limited to) a blood vessel, biliary tree, lung, esophagus, orintestine; as well as being based on the surrounding tissue structure.

FIGS. 15 and 16 show that continued twisting of the stent allow thebulbous sections of the stent to contract and expand, as with aperistaltic motion.

FIG. 17 shows the embodiment of FIG. 12 with a stretchable electrospuncovering.

FIG. 18 shows the covered embodiment of FIG. 17 twisted about ¼ turn tothe left.

FIG. 19 shows the twisted covered embodiment of FIG. 18 , wherein theends of the twisted stent have been pushed towards each other, causingthe flexible connectors and the covering to bulge outwards to maintainsurface contact. Twisting, pushing and pulling on (or of) sections ofthe stent are dependent upon the biomechanics of the lumen in which thestent is placed, including (but not limited to) a blood vessel, biliarytree, lung, esophagus, or intestine; as well as being based on thesurrounding tissue structure.

FIG. 20 shows that continued twisting of the covered stent allow thebulbous sections of the stent to contract and expand, as with aperistaltic motion.

EXAMPLE 1: DEPLOYMENT OF BIDIRECTIONAL SELF-EXPANDING STENT

An introducer sheath is inserted in an appropriate site in order to gainaccess to a vessel or lumen.

A guide wire is inserted through the introducer sheath and advancedthrough the vessel or lumen to span the area where the stent is to bedeployed.

The tip of a catheter device is advanced onto the guide wire and thecatheter device is advanced through the introducer sheath into thevessel or lumen. The catheter device is advanced through the vessel orlumen such that the tip of the catheter is advanced beyond thedeployment site and the stent is directly within the deployment site.

The protective sheath is withdrawn, thereby exposing the stent at thedeployment site and expanding the stent against the walls of the lumen.

Following deployment of the stent, the catheter device is withdrawn fromthe vessel or lumen. The guide wire and introducer sheath are removedand the incision at the entry point is sutured.

EXAMPLE 2: MANUFACTURE OF BIDIRECTIONAL SELF-EXPANDING STENT

The self-expanding bidirectional stents of the present application canbe made from nitinol, similar equi-atomic or near equi-atomicintermetallic compounds of nickel and titanium or other superelasticmetals or alloys. The stents can be made by any basic process, formedfrom a slotted tube, laser cut, formed, heat set, deburred and/orpolished by any method known in the art for the making or cutting ofnitinol stents. In particular embodiments, the self-expandingbidirectional stents of the present application are manufactured with adiameter that is larger than that of the target vessel such that, whenthe stent self-expands at the target site, it will hold itself inposition by pressure against the walls of the lumen.

The above description is for the purpose of teaching the person ofordinary skill in the art how to practice the present invention, and itis not intended to detail all those obvious modifications and variationsof it which will become apparent to the skilled worker upon reading thedescription. It is intended, however, that all such obviousmodifications and variations be included within the scope of the presentinvention, which is defined by the following claims. The claims areintended to cover the claimed components and steps in any sequence whichis effective to meet the objectives there intended, unless the contextspecifically indicates the contrary.

It is appreciated that certain features of the invention, which are forclarity described in the context of separate embodiments may also beprovided in combination in a single embodiment. Conversely variousfeatures of the invention, which are for brevity, described in thecontext of a single embodiment, may also be provided separately and/orin any suitable sub-combination.

What is claimed is:
 1. A bidirectional stent, comprising: acylinder-shaped stent body comprising a plurality of axially arrangedrows of struts encircling a central lumen and a plurality of axiallyarranged alternating rows of s-shaped connectors and rows of opposites-shaped connectors encircling the central lumen, wherein openings arebetween each of the s-shaped connectors arranged in alternating rows,and wherein each row of s-shaped connectors is flanked on both sides byrows of opposite s-shaped connectors and each row of opposite s-shapedconnectors is flanked on both sides by rows of s-shaped connectors,wherein each of said rows of struts consists of struts inter-connectedto form a wave-pattern with alternating peaks and troughs, wherein eachpeak has a tip and each trough has a bottom, wherein each peak in a rowof struts is connected at its tip to a peak at its tip in an adjacentrow of struts by an s-shaped connector or opposite s-shaped connector,wherein said s-shaped connectors in the same row of said s-shapedconnectors have the same configuration, and wherein when the stent is ina resting state, each peak in each row of struts is attached to one endof an s-shaped connector or an opposite s-shaped connector that isattached at its other end to a facing peak of an adjacent row with saidfacing peak being at an angle to said each peak, and each of saids-shaped connectors or opposite s-shaped connectors has a body having acontinuous curve with an inflexion point, and wherein when said stent issubject to twist, said rows of s-shaped connectors and opposite s-shapedconnectors contract or expand in an alternating manner to form aperistaltic shape in said stent body, and said rows of s-shapedconnectors or opposite s-shaped connectors that are contracting form aneck shape, and said rows of s-shaped connectors or opposite s-shapedconnectors that are expanding form a peristaltic shape, and said neckshape has a lesser radius than the radius of the peristaltic shape atits greatest expanse, thus allowing said stent body to be reversiblytwisted clockwise or counter-clockwise from one end of said stent bodyby a full turn without causing permanent deformation of said struts andsaid s-shaped connectors or opposite s-shaped connectors in said stentbody.
 2. The bidirectional twistable stent of claim 1, wherein each ofsaid s-shaped connectors has a length that is about 150% to 500% of thelarger of the row width of the two rows of struts that are connected bysaid s-shaped connectors.
 3. The bidirectional twistable stent of claim2, wherein each of said s-shaped connectors has a length that is about300% of the larger of the row width of the two rows of struts that areconnected by said s-shaped connectors.
 4. The bidirectional twistablestent of claim 1, wherein said stent body is covered with abiodegradable coating.
 5. The bidirectional twistable stent of claim 4,wherein said biodegradable coating comprises chitosan.